Grapefruit

Grapefruits contain: vitamin C, vitamin A, vitamin E, vitamin K, and the B-complex group of vitamins including folate, the antioxidant lycopene, calcium and potassium.
A study from the Nutrition and Metabolic Research Center Researchers believe that a flavonoid known as naringenin found in grapefruits is responsible for reduced insulin levels.
It is thought that this improved balance in blood glucose may curb appetite and reduce food cravings, consequently promoting weight loss and preventing diabetes. Having low levels of insulin is ideal as this means that your body can more efficiently use food for energy instead of storing it as fat.